TERRESTRIAL VISITORS

Triple Planetary Conjunction

February 15, 2008

Date: February 16-29Time: 6:15 pm, one hour before sunrisePlace: the southeastern sky

Yes, you’ll need to rise before the Sun to see this spectacle. We normally target an hour after sunset for our astronomy lesson, which is convenient for most people, but sometimes the best views are early in the day.

For most of this month, the planets Venus and Jupiter have been shining beacons in the morning sky near the “Teapot” constellation Sagittarius. During the last half of the month they’ll be joined by elusive Mercury. The chart above shows their February 16 positions. If you watch over a period of a few days, you’ll see Venus slip east (arrow), passing very close to Mercury on that date.

The word conjunction has a technical meaning related to astronomical coordinate systems. If you’re curious, look here. For the casual observer, suffice it say this means the planets will be very close. For the best view, find a clear horizon not blocked by mountains or buildings, as this trio is fairly low in the sky. Venus and Jupiter are especially bright; Mercury will be about as bright as the stars of the Teapot.

This dance of the planets is an ephemeral occurrence. All the planets drift through the sky with respect to the stars, moving from one constellation to the next. The stars, however, are fixed in their relative positions — the Teapot always looks like the Teapot. Fittingly, the word planet comes from the ancient Greek for “wanderer.”